Large diameter pipe is normally laid in sections that are joined together by means other than threaded joints. A typical system involves pipe sections having a spigot on one end and a bell on the other end. The spigot of one section is designed to telescope into the bell of the next adjoining section and the space between the bell and the spigot is filled with packing to prevent any leaks and contain the fluid to be carried in the pipe. Usually such pipe is laid in trenches, assembled and sealed in the trench, and then the trench is back filled with earth. Many problems have developed with such piping, which may be concrete, metal,plastic, or a combination of these. The packing and sealing usually is done by hand with the result that no two joints are assembled in exactly the same way, and they, therefore, have different strengths and weaknesses. Furthermore, the shifting and settling of the earth produces stresses that the joint cannot absorb. The use of cement grout produces a brittle joint that cracks under minor flexural stress and adheres to the precast pipe only with great difficulty. The slightest longitudinal stress easily produces cracks and fractures of the grout, particularly along the interface of the grout and the precast pipe section.
In more recent times there have been improvements suggested such as that of U.S. Pat. No. 4,226,444 to Bunyan in which two straight pipe sections are abutted with a sleeve encircling the butt joint. The sleeve is sealed at each end with an inflatable ring and the space between the rings is filled with an epoxy resin which is allowed to harden under pressure. The resulting joint depends on a thin cylindrical film of epoxy resin which readily breaks at the pipe interface when the pipe sections are placed under tensile and flexural stresses.
It is an object of this invention to provide a novel improved pipe joint. It is another object of this invention to provide a bell-and-spigot pipe joint having a keyway to be filled with grout. Still another object is to provide a method of laying an underground pipeline and sealing it after the pipeline has been covered with earth and stabilized. Other objects will appear from the more detailed description which follows.